nt_string_c — Remake the string library

nt_string_c is a custom implementation of a subset of the standard C string functions (libc-like behavior, no safety checks for NULL).

Project	nt_string_c
Open	2026-01-23 03:02 CEST (UTC+1)
Closed	Not closed yet

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Features

String length / duplication

• nt_strlen(const char *s) Returns the length of the string s (excluding the terminating '\0').
• nt_strdup(const char *s) Allocates and returns a newly created copy of s (caller must free() it).

String comparison

• nt_strcmp(const char *s1, const char *s2) Lexicographically compares s1 and s2. Returns < 0, 0, or > 0.
• nt_strncmp(const char *s1, const char *s2, size_t n) Same as nt_strcmp but compares at most n characters.

Character / substring search

• nt_strchr(const char *s, int c) Returns a pointer to the first occurrence of c in s, or NULL if not found. If c == '\0', returns a pointer to the terminating '\0'.
• nt_strrchr(const char *s, int c) Returns a pointer to the last occurrence of c in s, or NULL if not found. If c == '\0', returns a pointer to the terminating '\0'.
• nt_strstr(const char *haystack, const char *needle) Returns a pointer to the first occurrence of needle in haystack, or NULL. If needle is empty, returns haystack.

Memory operations

• nt_memset(void *s, int c, size_t n) Fills the first n bytes of s with byte value c. Returns s.
• nt_memcpy(void *dest, const void *src, size_t n) Copies n bytes from src to dest. Returns dest (requires non-overlapping ranges).
• nt_memmove(void *dest, const void *src, size_t n) Copies n bytes from src to dest safely when ranges overlap. Returns dest.

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libc-like behavior (important)

• These functions assume valid pointers: passing NULL results in undefined behavior (like libc).
• Returned pointers from nt_strchr, nt_strrchr, and nt_strstr point inside the original string (no allocation).
• nt_strdup allocates memory using malloc: you must free() the returned pointer.
• nt_memcpy is undefined for overlapping ranges; use nt_memmove for overlap-safe copying.

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Build

This project builds a static library:

make

Output:

• Library: build/lib/libnt_string_c.a
• Objects: build/obj/*.o

Cleaning:

make clean   # removes objects + dependency files
make fclean  # removes build directory
make re      # rebuild

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Usage

Example:

#include "nt_string.h"

int main(void)
{
    const char *s = "hello";
    char *dup = nt_strdup(s);

    /* ... use dup ... */

    free(dup);
    return 0;
}

Compile with:

gcc -I./include main.c -L./build/lib -lnt_string_c

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Project structure

.
├── include/
│   └── nt_string.h
├── src/
│   ├── nt_strlen.c
│   ├── nt_strdup.c
│   ├── nt_strcmp.c
│   ├── nt_strncmp.c
│   ├── nt_strchr.c
│   ├── nt_strrchr.c
│   ├── nt_strstr.c
│   ├── nt_memset.c
│   ├── nt_memcpy.c
│   └── nt_memmove
└── Makefile

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Standards / flags

• C standard: C89
• Recommended flags: -Wall -Wextra -Werror -pedantic -std=c89

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Roadmap (next)

• Continue to remake the string library functions for learning purposes

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License

This project is under BSD 3-Clause License